Ultrasonic transducers, in particular as are used in bonding machines, comprise the essential elements of at least one ultrasonic vibration generator (for example made up of piezo elements), a horn and a tool which is connected to the vibration generator by means of the horn.
The prior art discloses providing sensors on a horn of an ultrasonic transducer in order to control process parameters, for example the instantaneous ultrasonic power or the applied force, or to serve monitoring and, if necessary, adjustment purposes in a bonding process, and thus to effect quality assurance, in particular in bonding machines.
An ultrasonic transducer with sensor elements on the horn is known, for example, from EP 0 275 877. This document describes an ultrasonic transducer with a horn which is distinguished by flat portions, milled-out portions or other recesses in which sensors can be disposed. The document therefore describes disposing strain gauges in an upper and lower flat portion of the horn in order to measure the vertical deflection of the horn during a bonding process and to determine the effective bonding force from this variable.
The known arrangement has the disadvantages that the ultrasonic transducers, in this case the horn, have to be specially prepared for fitting sensors, for example by providing said milled-out portions, flat portions or other portions from which material is removed. Portions such as this ultimately affect the stability of the entire ultrasonic transducer, are complex in terms of production and, depending on the field of use, require specially adapted ultrasonic transducers. Furthermore, in the case of the known arrangements, the sensors themselves belong to the vibrating system, and this ultimately makes it more difficult to tune the vibration system.
Furthermore, the fact that existing ultrasonic systems and transducers cannot be equipped with sensors in the known manner in order to monitor process parameters should also be noted as a disadvantage.